The present invention relates to shock absorbers such as hydraulic shock absorbers that generate a damping force by controlling the flow of a fluid against the stroke of a piston rod.
In general, shock absorbers attached to the suspension systems of automobiles or other vehicles are arranged as follows. A piston connected with a piston rod is slidably fitted in a cylinder having a fluid sealed therein. In response to a stroke of the piston rod, the piston slidingly moves in the cylinder, causing a flow of fluid. The flow of fluid is controlled to generate a damping force by a damping force generating mechanism comprising an orifice, a disk valve, etc.
In a hydraulic shock absorber disclosed in Japanese Patent Application Publication No. 2009-281584, for example, a back-pressure chamber (pilot chamber) is formed at the back of a main disk valve constituting a damping force generating mechanism. A part of the flow of fluid is introduced into the back-pressure chamber to apply the pressure in the back-pressure chamber to the main disk valve in the direction for closing the valve. The valve-opening operation of the main disk valve is controlled by adjusting the pressure in the back-pressure chamber with a solenoid valve (pilot valve). With this arrangement, it is possible to increase the degree of freedom for adjusting damping force characteristics.
The following problems are associated with a shock absorber having a damping force generating mechanism comprising a main disk valve, a back-pressure chamber, a solenoid valve, and so forth as disclosed in the above-mentioned Japanese Patent Application Publication No. 2009-281584. That is, the related-art shock absorber is complicated in structure and high in parts count. It is also necessary to ensure dimensional and assembling accuracies and sealability for various component parts. Further, the related-art shock absorber requires wiring to the solenoid. Thus, various schemes are required to increase productivity.